1. Field of the Invention
The present invention relates to hands-free devices for telephonic communications. More particularly, the invention concerns controlling the send, end, and push-to-talk functions of a combination cellular telephone/two-way radio, with a button on a hands-free device.
2. Description of Related Art
“Hands-free” devices which permit having telephonic conversations without holding a telephone, are widely used. A hands-free device typically includes a small speaker which is placed near a user's ear, a microphone, and a cable for connecting the speaker and microphone to the telephone. Hands-free devices have been particularly useful with cellular telephones.
Generally, cellular telephones have a button for establishing communication connections, typically designated “send”, and also have a button for terminating communication connections, typically designated “end”. To establish a connection for a conversation, a user typically enters a telephone number on a keypad, or selects a number from a stored directory of numbers, and then presses the send button. When a user receives a call, which for example, may be indicated by the telephone ringing or vibrating, typically the user presses the send button to answer the telephone and establish a connection for a conversation. To end a conversation, the user presses the end button to terminate the connection.
Communications with cellular telephones are conducted in conjunction with a cellular telephone network which includes base stations, which wirelessly transmit information to, and receive information from, cellular telephones, and which are coupled to the public switched telephone network. Communications over cellular telephones are typically full-duplex, which means that both parties to the conversation can simultaneously send and receive information.
The functionality of two-way radios has been added to a cellular telephone network, and to specific cellular telephones that function with the network, in products known as Motorola's Integrated Digital Enhanced Network (iDEN™), and Nextel Communication's Direct Connect™. When using the digital two-way radio feature, a user selects the user identification number of another user from a directory, and then presses a “push-to-talk” (PTT) button on the combination cellular telephone/two-way radio in order to instantly transmit to the other user's cellular telephone/two-way radio, through the digital cellular telephone/two-way radio network. If the intended recipient of the transmission is in a service area defined by the cellular system operator, and has the two-way radio functionality of their cellular telephone/two-way radio turned on, and is not in another conversation, the intended recipient will hear the transmitting sender speaking immediately after the sender presses the PTT button, and without the delay of waiting for the receiver's telephone to ring and be answered. If a user attempts to commence a two-way radio conversation with another user that is engaged in a cellular telephone conversation, the user's cellular telephone/two-way radio will produce a tone indicating that the other user's two-way radio is not available. If a caller places a telephone call to the cellular telephone in a cellular telephone/two-way radio, while the two-way radio is being used, the caller will be forwarded to voicemail for the cellular telephone. When using the two-way radio function, a user must hold down the PTT button while speaking and transmitting to one or more other users, and must release the PTT button in order to receive and hear a transmission from one or more users. Thus, the PTT button controls the transmit/receive, talk/listen, function. This type of communication, in which a user cannot simultaneously transmit and receive information, is called half-duplex, and is in contrast with cellular telephone communications, which are full-duplex. To permit usage of the two-way radio function, combination cellular telephone/two-way radios have a PTT button on the combination cellular telephone/two-way radio.
A known type of hands-free device for a two-way radio includes two cables attached to a common plug, which connects to the two-way radio. A PTT button is attached to the end of the first cable, and a microphone and an earbud (a small speaker which is placed in the user's ear) are attached to the second cable. Due to the second cable required for the PTT button, this type of hands-free device has proven inadequate for many applications. This type of hands-free device is also inadequate for use with a combination cellular telephone/two-way radio, because the microphone and earpiece in this type of device do not function with a combination cellular telephone/two-way radio, and because this type of device does not have the ability to control the send or end cellular telephone functions. Hands-free devices for cellular telephones have also proven inadequate for combination cellular telephone/two-way radios, because they lack a button that has the ability to control the two-way radio PTT function.